There's a LOT involved in those questions, but I'll try to keep it brief. I'll give a few sources, but if I start linking extensively this post is going to run very long. Just know there's much more info that can be easily found from sources like the UN and humanitarian agencies like Amnesty International.

• Hamas (the government in Gaza and a terrorist organization) would happily wipe out Israel given the chance. Israel's stated goal right now is to wipe out Hamas, but in reality they are killing a lot of Palestinians regardless of affiliation. For many years Israel + OPT (Occupied Palestinian Territories) has been an Israeli-governed apartheid state that oppresses Palestinians. So neither are good guys, although Hamas only has about 20-40k militants and it's not definitely not fair to say the millions of Palestinians are all Hamas. In metrics like taking land, killing people, illegal taking of prisoners and abuse thereof, starvation, etc. Israel is many times worse in terms of numbers and has been for a long time (like well over a decade).

• Iran is involved because extremists want to destroy Israel for reasons like religion and reducing Western influence in the region. Iran also funds militias like Hezbollah that attack Israel.

• Peace is nearly impossible because of a long, long history of violence in that region. Also, to a certain extent this situation of hatred is actually the plan. Israel made sure Hamas got funding because Israeli leaders like Netanyahu found it convenient to have a "boogeyman" to fuel fear and keep Gaza and the West Bank divided.

• The last serious attempt at peace between Israel and Palestine was probably the Oslo Accords, but it was always controversial and didn't work. Neither side kept 100% of their promises, and the Israeli Prime Minister Yitzhak Rabin was assassinated by an Israeli because of the Oslo Accords. There was still some support for peace following that assassination, but in the end it didn't materialize.

• The USA is involved because Israel is considered a long-term ally in the volatile Middle East region. Plus there's a LOT of money going both ways. Plus there are a lot of Christians in the US (AFAIK mostly Evangelicals) who legitimately believe that Israel must conquer all land promised to them in the Bible in order for Jesus to return and they vote. Plus it's huge business for industries like arms manufacturers. I'm also sure there are US voters who believe Israel is the moral choice, either because they don't know the facts I've touched upon or choose to ignore/accept them.