It's interesting that you subscribe to romantic nationalism. Though its dangers have been well-documented, I will concede it has its advantages as well, at least on the surface.
However, your assertion that patriotic Jewish Russians are an impossibiliity is both disturbing, dangerous and insulting. I do not say this to be rude to you, but to express my honest opinion.
First, the obvious point is that being a patriotic Jewish Russian is not only possible, but exists. Judaism is a religion; as such it is a sub-culture, not a meta-culture. We both agree that being Jewish means a lot to Jews; so does being a Christian mean a lot to Christian. But, if you assert that it is impossible to be a patriotic Jewish Russian, then you must, by extension, assert it is impossible to be a patriotic Protestant Russian, because Russia's religion is Eastern Orthodox. Or a patriotic Catholic Russian (not sure if such a thing exists, but I'm sure there are Catholic Russians somewhere ;p ). Or even a patriotic atheist Russian. These are all subcultures that mean a lot to their members; they do not subtract loyalty to the mother country, though, which I think is what concerns you.
I agree that if one's first loyalty is to Israel (or any other country), then one should move to Israel and become an Israeli, or whatever country your first loyalty is to. But it is entirely possible to be sympathetic and supportive of another state, or a foreign cause, without owing them your primary allegiance.
Asserting that one cannot be a patriot if one is religious is a ridiculous assumption. In fact, the two often go hand in hand. In America, many, even most, patriots I know are all religious, to one extent or the other, and proudly identify with one faith's denomination in particular. Just as I am sure that in Russia, there are many patriots who are religious; Eastern Orthodox, Protestants, and Jews.
One cannot convert to Russianism, as Russia is a country, not a faith. One could convert to the Eastern Orthodox Church. One could immigrate to Russia. And one could assimilate there; although, with attitudes like yours, it seems like that would be hard.
But, if you assert that it is impossible to be a patriotic Jewish Russian, then you must, by extension, assert it is impossible to be a patriotic Protestant Russian, because Russia's religion is Eastern Orthodox. Or a patriotic Catholic Russian (not sure if such a thing exists, but I'm sure there are Catholic Russians somewhere ;p ). Or even a patriotic atheist Russian. ==
IHMO Judaism is not similar religion as Christianity: Ortodoxism or Protestamtism. Judaism is the ethnical religion for only one nation. People who wasn't born by jewish mother cann't become true jew so exercise Judaism.
If it wasn't so we should see today that Judaism was the world religion like Christianity but it isn't.
SO there can be patriotic Russian with Protestant religion and even ateists but hardly Judaists. Since Judaists has to be alligent only to Israel. Christiants can with different ethnic origin but not Judaists.
One cannot convert to Russianism, as Russia is a country, not a faith. One could convert to the Eastern Orthodox Church. One could immigrate to Russia. And one could assimilate there; although, with attitudes like yours, it seems like that would be hard.==
Russianry is the ethicity. Russia as the country is the national home of Russian people and allied nations who invested thier lands to Russia territory.
One cann't be hard to become Russian if he trully want. Russians doesn't follow the purity of blood or the birth of russian parents. One may become Russian if he doesn't have even drop of Russian blood.
Accually Russians itself are bunch of assimilated tribes. Partly finno-hungarian tribes, partly eastern slav tribes and partly turks. Even some asian (former mongols) and african people became Russians. But all them are assimilated means they are not follow thier origin matters.
Jew can become Russian with easy but he should completely forfeit his Judaism.