Nice question; but, it appears to be the WRONG one.
Has MORMONism ever butted heads against the United States Government?
...the presidential campaign of Mormon Church founder Joseph Smith in 1844: “Challenging Democrat James Polk and Whig Henry Clay, Smith prophesied that if the U.S. Congress did not accede to his demands that ‘they shall be broken up as a government and God shall damn them.’
Smith viewed capturing the presidency as part of the mission of the church.
Well...
Isn't THIS interesting!!
You mean, like, had a war?
A war against the United States? The Mormon War/Utah War? From 1857 to 1858? An armed rebellion? Where there wasn't a lot of shooting going on, and it was pretty much a standoff (except for those 120+ civilian men, women, and children murdered on September 11, 1857, and the six civilians murdered at the Aiken Massacre the following month - I don't count the people killed by the Northern Paiute at Fort Lemhi as part of the war).
That kind of butting heads against the U.S. Government?
Ummmm. Yes, speaking historically, it has.