The White House has attributed President Trump’s slurred speech to a dry throat.

The White House has attributed President Trump's slurred speech to a dry throat, notes the Los Angeles Times.
His enunciation trouble came at the end of his Wednesday announcement that the U.S. intends to acknowledge Jerusalem as Israel's capital and will be moving its embassy there. 
While making his closing remarks, he appeared to slur his speech, drawing out the first s in United States.
"His throat was dry. There's nothing to it," Raj Shah, a White House spokesperson, said.
In the moments following the president's trouble speaking, Twitter was flooded with messages of concern, both real and feigned in the service of sarcasm. 
Aaron Rupar of ThinkProgress wrote, "Trump could barely articulate words by the end of his speech. Sad," and, "Trump is struggling through a rough case of dry-mouth yet again." 
"Worth listening to the end of that Trump thing again...got a bit angry, belligerent and even slurred speech," journalist Allen McDuffee tweeted. "Something wasn't right." 
Mia Farrow joined the conversation, asking, "Why is Trump slurring his speech?"