Yes, if you joke about 'murdering the head of state' - any reasonable state is probably going to look into it. But in this case, joking about a historical even

Yes, if you joke about 'murdering the head of state' - any reasonable state is probably going to look into it. But in this case, joking about a historical event, inviting a foreign country to invade is way beyond reality, obviously. So, if you invited the 'Germans to invade America' again, nobody will come knocking except the Twitter Nazis. (Pun intended).