After tumbling in April amid concerns over US President Donald Trump's global tariff campaign, the S&P 500 Index (SP: .INX) has come roaring back.

The benchmark US stock market index closed yesterday at 6,299.19 points.

While that's down 1.4% from the all-time closing high of 6,389.77 points, notched on 28 July, the S&P 500 has rocketed 26.4% since the 8 April close.

For some comparison, the S&P/ASX 200 Index (ASX: XJO) has gained 20.1% since its own recent lows on 7 April.

That outperformance becomes more marked if we take a step back.

Over the past five years, the ASX 200 is up 46.9% while the S&P 500 has soared 88.0%.

Clearly then, it's paid to have at least some of your investment eggs nestled in the US stock market.

Of course, these gains have all come on gone.

The million-dollar question now is, can the US stock market keep marching higher into 2026?

For some greater insight into that question, we defer to Nicole Inui, head of equity strategy for the Americas at HSBC (courtesy of The Australian Financial Review).

What now for the S&P 500?

Pointing to what's motivating investors in US stocks, Inui said it's the "excitement around AI and policy shifts".

This has seen tech stocks broadly outperforming other stocks on the S&P 500.

According to Inui:

Both groups of stocks have rallied since 'liberation day', but tech has outperformed and rightly so. The tech rally has been driven by fundamentals. Earnings growth is tracking near 20% for 2025 with positive momentum as earnings revision ratios move higher.

On the other hand, for the 'rest' of the market, earnings growth and momentum is slowing. Financials are the notable exception.

And Inui expects the AI trend to continue to drive investor interest.

"We have more confidence in the sustainability of the AI trade than further easing on policy uncertainty. Earnings releases from key stakeholders continue to tout the benefits of AI and its positive impact on results," she said.

As for where the S&P 500 is heading next, HSBC's bear case sees the index falling 9.5% to 5,700 points if Trump's tariffs "drive corporate profits lower and inflation higher".

The broker's base case sees the benchmark US index at 6,400 points, or about 1.6% above current levels. That's based on 2025 earnings growth of 9%, with the impact of US tariffs on corporate profits "offset by continued strength in tech".

Inui said HSBC's bull case "assumes AI adoption accelerates while suppliers bear much of the tariff costs". In this case, the S&P 500 could gain another 11.1% from current levels to reach 7,000 points.

Can I invest in the US stock market on the ASX?

There are a number of ASX-listed exchange-traded funds (ETFs) that are intended to track the performance of various US markets.

For the S&P 500, you might want to look into the SPDR S&P 500 ETF Trust (ASX: SPY).

The ASX ETF's largest holdings include Nvidia Corporation (NASDAQ: NVDA), Microsoft Corp (NASDAQ: MSFT), Apple Inc (NASDAQ: AAPL), and Amazon.com, Inc. (NASDAQ: AMZN), to name a few.