[Seraph]

US had to get involved in WW2 or the Germans and Japanese might have won the war.

How does that change the fact that the US took a very agressive stance vs. the Germans?

Kennedy wasn't very agressive and only tried to invade Cuba during the Cuban Missle Crises.

The Bay of Pigs invasion (April 1961) predates the Cuban missle crises (Oct 1962).

The Vietnam War was acually started back in 1958 when Dwight D. Eisenhower(Republican) was president. Kennedy wanted the troops to be pulled out of Vietnam but that didn't happen because he got asassinated. When Richard Nixon(Republican) became the president in 1969, he had more troops pulled into Vietnam and there was more heavy bombing.

On May 8th 1960 there were 685 non-combat troops to Vietnam.
On Feb. 7th 1962, American military strength reaches 4,000.
On Nov. 15th 1963 (a week before Kennedy was shot) there were 15,000 troops in Vietnam. 1,000 of which were schedualed to be withdrawn.
At the end of 1964, US troop strength was 23k.
At the end of 1965, US troop strength was 181k.
At the end of 1966, US troop strength was 385k.
At the end of 1967, US troop strength was 486k.
At the end of 1968, US troop strength was 536k.
Nixon becomes president, and lo and behold, troop strength goes down!
At the end of 1969, US troop strength was 474k.
At the end of 1970, US troop strength was 335k.
August 12th 1972, The last American ground combat troops leave South Vietnam; 43,500 airmen and support personnel remain.
August 29. President Nixon announces withdrawals that will reduce total US strength in South Vietnam to 27,000 by December 1st.
January 15. Because of the progress in talks between Dr. Henry Kissinger and Le Duc Tho initial an agreement ending the war and providing for the release of prisoners of war; the agreement is formally signed on 27 January.

So, Nixon reduces troop strength, and ends the war, and you call that "troops pulled into Vietnam."

I'd recomend "Vietnam Order of Battle" by Shelby L. Stanton for information on the troop buildup.
This site has a graph showing the trend in troop strength

As for the bombing:
I don't have access to the actual number of sorties, but the heavist day of bombing of the war occured on Sept 12th 1966, and December 12th 1966 has the record for most planes downed in a day. Both of these fall squarely in the Johnson presidency.

Ronald Regean had a ton of money spent the armed forces during the end of the Cold War that it almost bankrupted the U.S. economy.

How does this qualify as "[being] more aggressive and start[ing] more wars"?

The increase in military spending between 1980 and 1988 was about the same as the increase in spending on Social Security and Medicare (154.1 vs. 151.4 billion dollers Source). In 1980, the US budget was 30% of GDP, in 1988 it was 30.4%, this is not the kind of change that bankrupts a government. Source

Trying to blame the increase in debt durring the 80s on increased military spending is, quite simply, wrong. The increase in Social Security and Medicare, Regans love of supply side economics durring his first few years, and the screwed up economy he inherited (which is more the fault of Nixon/Ford than Carter) all played their parts.