Depending on who's numbers you want to accept, somewhere between 50,000 and 120,000 convicts were transported to America before the revolution. That represents roughly an equal number of people to slaves.
Easily, an equal number of people voluntarily entered into indentured servitude to come to America in that same period. Estimates run as high as 250,000 people entered into contracts for 3 to 10 years servitude (essentially slavery) in exchange for passage to America before the revolution. Indentured servants were usually treated no better than other slaves and race mattered little to most owners. Interestingly, included in these numbers are a significant number of Indians (from India) and Asians, although most ended up in Caribbean colonies rather than the US.
Also of note is that early slaves, including Blacks from Africa, were usually enslaved as indentured and had a term of service after which they were freed. It is only later, particularly after the US government stopped allowing importation of new slaves in 1807 (US ships were prohibited from slave trade in 1794) that slavery became unconditional and endless due to lack of access to a market to get new ones.
As for building America. That's clearly nonsense. Slaves were unskilled labor almost entirely. What indentured servants got apprenticed as part of their service only would lead to their becoming skilled journeymen on release. That was a distinct minority. Mass labor in and of itself is worthless unless organized, equipped, and led by others with a range of skills and abilities to utilize that labor.
