The weekend's air strikes marked the biggest intervention by Western countries against Syrian President Bashar al-Assad and his ally Russian Federation, which is facing further economic sanctions over its role in the conflict.
US stocks closed broadly higher Monday, adding to the market's gains from last week.
Stocks declined on Friday amid strong bank earnings that failed to impress investors, but the market secured weekly gains as Wall Street shook off concerns over USA trade.
The Dow Jones Industrial Average dropped 122.81 points, or 0.5%, to 24,360.24.
Stocks climbed before the speech, boosted by positive earnings and a positive economic data.
The S&P 500's technology sector.SPLRCT was the biggest boost to the benchmark with a 0.8-percent increase followed by the healthcare index.SPXHC which was up 0.97 percent.
Merck (MRK.N) rose 2.2 percent after the company presented positive data on its cancer drug Keytruda, also boosting the S&P healthcare index.
Bucking the trend in the FTSE 100 and posting its biggest gain were shares of Whitbread, closing 7.2 percent higher in London.
Shares of optical components makers, including those of Acacia Communications (ACIA.O) and Oclaro (OCLR.O), took a beating after Reuters reported that the USA government was banning American companies from selling components to Chinese telecom equipment maker ZTE Corp 0000063.SZ(0763.HK). Acacia slumped nearly 36 percent, compared with a 15.2-percent drop for Oclaro.
JB Hunt Transport Services (JBHT.O) jumped 6.6 percent after the trucking company's profit topped estimates.
"Strong client activity, coupled with a growing global economy and solid USA consumer activity, led to record quarterly earnings", Brian Moynihan, Bank of America's chief executive officer, said in a statement.
Netflix (NFLX.O) fell 2 percent.
Hedge fund Elliott Advisors has become the second activist investor to call for Whitbread to split its hotel and coffee shop businesses after emerging as the largest shareholder in the British company, Reuters reported.
Advancing issues outnumbered declining ones on the NYSE by a 2.75-to-1 ratio; on Nasdaq, a 2.04-to-1 ratio favored advancers.
The S&P 500 posted 11 new 52-week highs and no new lows; the Nasdaq Composite recorded 68 new highs and 36 new lows.