Tautology. "Excessive" anything means "too much," and that's always bad. However, the determination of the "excessive" quantity of anything is subjective.
Ours is not a Catholic country but a country which has mostly treated Catholics quite well. We Catholics have returned the favor by ever refreshing this nation with lean and hungry immigrants often of great talent and determination.
You claim it to be an "OBJECTIVE truth that excessive immigration is bad." Actually, that is the SUBJECTIVE view of the "blood and soil" types who pose as conservatives (Paleo"conservatives" actually). The Rockford Institute has very little to do with actual conservatism. Nor do any other "paleo" institutions. They are collectively a platoon of social eccentrics (think of the Teddy Roosevelt character in Arsenic and Old Lace continually charging up the stairs of his aunts' Brooklyn House under the delusion that he was charging up San Juan Hill) with the foreign policy of old Neville Spineless Chamberlain, the racial enlightenment of the old White Citizens' Council (now the "Conservative" Citizens' Council whose newspaper was edited by the late Sam Francis of "National Renaissance" fame), the social issues and immigration policies of such outfits as FAIR which is dominated by Planned Barrenhood, NARAL and ZPG enthusiasts.
This "blood and soil" dementia belongs in Otto von Bismarck's Germany not in our country or in various little comic opera nations in Europe contemporaneous to Bismarck. The revolutions of 1848 were over questions such as whether mature adult citizens would continue to be told whether and whom they might marry by the local comic opera poohbah such as a German Landgraf (the $64 term for pushy pseudonoble buttinsky). My ancestors in Germany in one family line decided that they would make their own decisions on marriages and other matters with no need for Landgrafs. They came to southern Indiana and farmed with or without "papers." The great-grandmother born to that family married a great grandfather who stowed away on a boat from Germany to Baltimore and was caught and made to work his passage (very likely landing and entering the country "without papers"). No one in my family ever gave a rat's patoot for whether these German ancestors ever had "papers."
I could bore you with the details of the other branches of my family and their entrances to the US very likely "without papers." I won't. I sincerely hope that not a single one paid homage to the bureaucratic pedigree gods and that not a single one had "papers."
My family has not been notably enthusiastic to serve in the military but no one has yet refused service either. My mother's brother was killed in the sinking of destroyer USS Buck off Salerno by a Nazi U-Boat in WWII. My father and all my uncles served in that war as well. A few relatives were in WW I. A few served in the Korean War and Vietnam War. It is their service and not some useless bureaucratic immigration paperwork that ought be the standard of citizenship. A Mexican willing to serve in our military in service to our nation's purposes is far better qualified in citizenship than some whiny anti-American anti-war leftist college professor or faux intellectual whose ancestors have been citizens for generations. The Mexican-American soldier loves the USA as much and as enthusiastically as the leftist or paleo"conservative" despises the USA. The former makes a far better citizen.
The genuine Catholic (like many other good citizens) has little problem with authority. The Roman Catholic Church is all about Authority and submission to it and not at all the Kumbaya communes that claim Catholicism. One's Americanism is more about one's ideology and, often, one's theological views than about one's street address in a mobile society such as ours. Who my grandmother was or what her neighborhood was may be considerably less important in the formation of MY citizenship than what her religion was and what her politics were. For the sake of discussion, she was a hard core Catholic from Cork who was an enthusiast for wars fought in her time, considered herself a liberal Democrat (as defined in about 1915 in Boston in service to James Michael Curley) and a bit feminist but who would have strangled abortionists with her bare hands three-at-a-time with glee. All of that is why immigration of Catholics (real Catholics) to America is a good thing OBJECTIVELY. That applies to many others as well. No one ever designed the United States to be a Catholic nation. The USA will, however, not suffer from becoming a somewhat more Catholic nation than it is now, especially if the incoming Catholics are more Catholic than our domestic ones tend to be. Nor will the USA suffer from becoming, for example, a more Evangelical nation, a more Orthodox Jewish nation, a more Eastern Orthodox nation. If there is any "blood" there, it is one's family and not one's nationality. There is no soil. There is plenty to qualify one as an American in the way of ideas and behavior without wondering whether a Mexican soldier in the US Army had ancestors fighting under Zachary Taylor or under Santa Ana in 1848.
The United States is a dynamic nation with a wonderful, if occasionally flawed, and proud history. The future should be likewise. We are a nation and not a museum. We are homogenized nor pasteurized as a nation. Had we been either, we would be a museum, with a brilliant past and stultifyingly boring present reality like much of what Rumsfeld accurately derided as "old Europe." The amazing thing about "old Europe" is how very much it proves day by day not to have been worth saving. Today, the Japanese are among our closest allies and strongest supporters. With the occasional exception of a Winston Churchill, a Margaret Thatcher or a Tony Blair, Europe (outside of the Vatican) has been generally useless since WW II. They want their own freedom (to some small extent) but don't care about anyone else's. When France falls to Islam, I hope we let them grovel for a few years while we throw the insolent words of Chirac and de Villepin back in their faces before Uncle Sugar comes to the rescue of the French. We should let them know it is the last time we save their useless backsides unless they closely follow our foreign policy and military lead thereafter.