Is it possible to love a stranger?

Humanly speaking , no: it needs the 'agape' love of God to be able to love a complete stranger, but with the indwelling Holy Spirit of God given to all born-again Christians that is possible. Indeed, it is not only possible but commanded:-

Mat 5:43 You have heard that it was said, "You shall love your neighbor and hate your enemy."

Mat 5:44 But I say to you, Love your enemies, bless those who curse you, do good to those who hate you, and pray for those who despitefully use you and persecute you,

Mat 5:45 so that you may become sons of your Father in Heaven. For He makes His sun to rise on the evil and on the good, and sends rain on the just and on the unjust.

Mat 5:46 For if you love those who love you, what reward do you have? Do not even the tax-collectors do the same?

Mat 5:47 And if you greet your brothers only, what do you do more than others? Do not even the tax-collectors do so?

Mat 5:48 Therefore be perfect, even as your Father in Heaven is perfect.

Mat 22:37 Jesus said to him, You shall love the Lord your God with all your heart, and with all your soul, and with all your mind.

Mat 22:38 This is the first and great commandment.

Mat 22:39 And the second is like it, You shall love your neighbor as yourself.

Mat 22:40 On these two commandments hang all the Law and the Prophets.

Luk 10:25 And, behold, a certain lawyer stood up, and tempted him, saying, Master, what shall I do to inherit eternal life?

Luk 10:26 He said unto him, What is written in the law? how readest thou?

Luk 10:27 And he answering said, Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy strength, and with all thy mind; and thy neighbour as thyself.

Luk 10:28 And he said unto him, Thou hast answered right: this do, and thou shalt live.

Luk 10:29 But he, willing to justify himself, said unto Jesus, And who is my neighbour?

Luk 10:30 And Jesus answering said, A certain man went down from Jerusalem to Jericho, and fell among thieves, which stripped him of his raiment, and wounded him, and departed, leaving him half dead.

Luk 10:31 And by chance there came down a certain priest that way: and when he saw him, he passed by on the other side.

Luk 10:32 And likewise a Levite, when he was at the place, came and looked on him, and passed by on the other side.

Luk 10:33 But a certain Samaritan, as he journeyed, came where he was: and when he saw him, he had compassion on him,

Luk 10:34 And went to him, and bound up his wounds, pouring in oil and wine, and set him on his own beast, and brought him to an inn, and took care of him.

Luk 10:35 And on the morrow when he departed, he took out two pence, and gave them to the host, and said unto him, Take care of him; and whatsoever thou spendest more, when I come again, I will repay thee.

Luk 10:36 Which now of these three, thinkest thou, was neighbour unto him that fell among the thieves?

Luk 10:37 And he said, He that shewed mercy on him. Then said Jesus unto him, Go, and do thou likewise.

It may help to think of 'love' as kindness or mercy or compassion .