The northern San Diego community of La Jolla, California. The new tax code may lead to ‘downward pressure on housing prices’ in high-cost states, such as California, according to expert.

A year into President Donald Trump’s term, the overall U.S. housing market remains strong. But uncertainty also looms large, experts say, noting effects of the new tax law could bring big changes.

“The most overused phrase in real estate used to be ‘location, location, location,’” said Jonathan Miller, president of the real-estate appraisal firm Miller Samuel. “Now it’s ‘uncertainty.’”

That uncertainty existed at the end of both 2016 and 2017, albeit for different reasons.

Mr. Miller, who is also the author of market reports tracking many major cities and towns around the U.S., said there was a pause in activity at the end of 2017, although the official numbers are not yet available.

“Late 2017 and 2016 were both characterized by a pullback or pause in the market,” Mr. Miller said. “In 2016, it was the heated final days of the election. In 2017, there was a pause during the conversation about the new tax bill and what the ramifications for housing would be.”

Once those events were in the rear window, buyers felt more comfortable making deals they had been hesitating to make.

“It’s not so much what the event was, just that it’s over,” Mr. Miller said. “Once people can get their arms around it and make calculations, they can re-enter the market.”

Mr. Trump’s lack of political experience may continue to hold some potential buyers and sellers back. But short of engaging the U.S. in war or implementing another huge executive change, his agenda isn’t necessarily having an effect on the market, said Andres Carbacho-Burgos, head of the residential real estate team at Moody’s Analytics.

“He is pretty much in line with the Republican Party,” he said. “So it’s more a question of what the party will do, rather than put it all on Trump.”

And it could be up to two years before the effects of any policy changes made during his administration will be manifest in the U.S. real estate market, Mr. Andres Carbacho-Burgos said.

For now, the market hasn’t seen too much change.

Housing remains healthy

In general, the U.S. housing market is healthy, experts said, and has been steadily improving for years.

“There’s still strong demand. We still have dirt-cheap interest rates,” said Nela Richardson, the chief economist at Redfin.

There were 1.7% more home sales in 2017 than there were in 2016, the last year of former President Barack Obama’s administration, according to a Redfin report. Prices gained 7% over the year, the report said. This rise is part of an ongoing trend, as the housing market continues to rebound from the recession of the late 2000s.

One thing that remains the same under both presidents is a lack of supply.

“What the housing market had been starved for under President Obama was inventory,” Ms. Richardson said. And she doesn’t expect that to change in 2018.

The number of homes for sale declined 14.5% in December, compared to the year before,…