Bull-dozing the Colosseum (built by slaves, including those captured during the destruction of the Temple in Jerusalem, possibly upward of 100,000 jews) is not equivalent to celebrsting the building of the Colosseum.
The 4th of July celebrates not just the founding of the US, but the monsterous Imperial project it has become. It is a distraction to the crimes committed today by your government (murder via drone strikes? Torture and unlawful imprisonment? Continued occupation of Puerto Rico and Hawaii... To name but a few). The 4th celebrates all the good things about the US, freedom of speech, and equality of all citizens (assuming you don't want a right to a fair trial, and are either Japanese-American during the war, or Black and walking down the street today...), it celebrates the incredible advances capitalistic free markets have brought the world (assuming you aren't working for below minimum wage as a migrant worker, or struggling to make ends meet, to pay college tuition, or to cover your own healthcare costs...). The freedom and protection of the world from the Soviet menace (i will not defend the soviet union, as they were amongst the worst authoritarian murders in history, but i will likewise not defend the proppin up of dictators in south america by the CIA, or the toppling of socialist/left leaning governments, and anyone who opposed US corporate interests... Nor the infiltration, assassination and undermining of left-leanjng activists and community organisers by the FBI - see the Church committee and cointelpro, where the US security/intelligence services used political policing to undermine the right to organise, the right to protest - which you'd think the 4th of July celebraters would be appaled by - the right to engage in the democratic process).
It is not just indigenous peoples, robbed of their lives and land, who should reflect on what this day means. It is every person touched by the biggest Imperial project of the 20th century.