Not directly as a retail investor. US‑domiciled mutual funds are generally off limits because of European and UK regulations like PRIIPs and UCITS. Use UK‑available funds that track the same idea, or go global as we do.

The closest to the equivalent of VTSAX is Vanguard US Equity Index Fund

We buy Vanguard FTSE Developed World Ex UK and the Vanguard FTSE Global All Cap