How are the US and other countries going to punish them considering that the country is a sovereign nation?
The US will do whatever it likes, the only consideration is likely whether any action will have a negative effect on any US allies - although this would likely be a minor consideration, and not sufficient to sway a decision.
The US under Trump however is less interested in international affairs than is normally the case, so is perhaps less likely to act.
The USA has no power over any country's presidency they can not dethrone any sitting President
I'll quote my
9/11 example again.
the U.S. won't retaliate over someone getting elected, but only if someone has control over a country that poses a direct national security threat.
It's a grey area though, 'direct national security threat' can and does mean anything. Similar to how Department of Defense is all about attack rather than defence.
I'll add again - nothing against the US here, it's just how the most powerful nations have always behaved.