Why can the United States repeatedly open fire on another sovereign country? Targeted killings? Counter-terrorism operations?

Basic quotes from the US:
“Those who sit at the table don’t need to listen to the menu.”
“Dignity exists only on the edge of the sword; truth is only within cannon range.”
“Better to strike once than to be hit a hundred times.”
“Start the fight in the morning, issue ID cards in the afternoon.”
“A small country that does not act humble, weak but not afraid of the strong, insulting neighbors without reason, and foolishly greedy in alliances, may perish.”
“This season, the US is terrifyingly strong.”
“Do you know what the consequences are of angering a major power?”
“Why build a country on American oil fields?”
“The US needs a war to showcase its strength.”
“Anyone who offends the mighty US, shall be punished no matter how far away!”
“Do you know what a ‘Yichang’ is?”
“Watch closely, only perform once.”
“Seeing America act so rogue, I feel at ease.”
“1h22m, a battle that makes a legend.”
“What is international law? Just a pile of worthless paper.”