First, I'd say you're just playing definition games with "confederate" and "major battle."
In reality, Maryland was a Union state which suffered not one but four different Confederate invasions -- May '62, September '62, June '63 and July '64.
These resulted in three major battles -- Front Royal, Antietam/Sharpsburg & Monocacy -- causing 25,000 casualties on both sides, 4,000 of them killed.
In every Confederate march into Union territory -- without exception -- troops "lived off the land" taking what they needed, often destroying what they thought useful to the enemy, sometimes "paying" for "requisitions" with worthless Confederate money.
Yes, slave-holding families did often welcome Confederate troops, but Union states remained loyal precisely because slave-holders outnumbered non-slave-holders several to one.
These Unionist families no more welcomed Confederate troops than most Confederacy families welcomed Union troops.
Pennsylvania suffered not one but three different Confederate invasions -- 1862, 1863 & 1864.
The Battle of Gettysburg (1863) was the war's largest, resulting in 50,000 casualties including 7,000 killed.
The 1862 and 1864 invasions did not result in major battles, but did leave trails of destruction, pillaging and even kidnappings of civilians.
Union states of Kentucky and Missouri both suffered from major and minor Confederate military operations throughout the war, suffering untold casualties and property destruction.
The Union state of Kansas suffered the Lawrence Massacre and Battle of Baxter Springs in 1863, plus a series of battles (Trading Post & Mine Creek) in October 1864 between Confederates under Price and the Union under Pleasanton.
These were not "major" by Virginia battle standards, but did include thousands of troops and hundreds of casualties.
They were certainly "major" to everyone involved.
Union state of Indiana suffered small Confederate raids from Newburg (1862), Hines (1863) and a larger one by Morgan (1863), with Morgan's raid moving on to Ohio, eventually involving many thousands of troops.
Union territory of Oklahoma saw battles throughout the war, beginning at Round Mountain in November 1861, ending in Stand Waite's final surrender in June 1865.
These typically (i.e., Honey Springs) involved thousands of troops with hundreds of casualties.
Union New Mexico and Arizona territories suffered a Confederate invasion in 1862, leading to the Battle of Glorietta Pass involving a few thousand troops and a couple of hundred casualties.
Smaller Confederate units (dozens to hundreds) operated in California and Colorado, while what we would call "special operations" teams attacked infrastructure in Vermont and New York.
Another planned Confederate invasion into Illinois was cancelled in 1862 after Grant's victories at Forts Henry and Donelson in Kentucky made invading Illinois impossible.
Bottom line: it's just not controversial to point out that Confederate forces invaded and operated in every Union state or territory they could reach with as many forces as they had available.
Most fought battles, and all left trails of pillage and destruction.
Total casualties from all these invasions were tens of thousands, including thousands dead.
To those people, there was nothing "minor" about it.
Which of these battles might be classified as "major" is irrelevant to the fact that Confederates always did what they could with whatever they had.
Finally, again: all this data is readily available by googling for example, "US Civil War Kentucky" which produces a long list of articles on that state's role in the war.
“battles might be classified as “major” is irrelevant”
It’s not irrelevant that some battles are major and some are not. All battles with more casulties than First Manassas is an objective standard.